DESCRIPTION (APPLICATION ABSTRACT): Nurses and others claim that low nurse staffing, increased use of overtime and per diem agency nurses, and other changes in hospital working conditions are putting patients at greater risk of avoidable adverse outcomes. These concerns have led to strikes and calls for hospitals, accrediting agencies, payers, and government to act to increase staffing and reduce overtime. Research has found a relationship between adverse outcomes and nursing skill mix and, to a lesser extent, nursing hours, but to respond to the issues now being raised, understanding of the relationship of nurses' working conditions to adverse outcomes needs to be substantially expanded. To achieve this, we will: Aim 1: Examine the relationship between adverse outcomes and use of overtime and contract nurses. Aim 2: Adapt methods used to measure other conditions in the nurses' work environment affecting staffing and workload in unit-level studies for use in hospital-level studies. These include: nursing care delivery models, job strain, and risk of injury. We will examine the independent effects of these variables on patient outcomes and their confounding effect in studies of staffing levels and mix. Aim 3: Examine the causal pathways through which elements of the work environment interact and influence patient outcomes. To address these aims, we will a) construct outcomes from hospital discharge datasets, b) obtain data on nurse staffing levels, mix, overtime, and contract hours from State administrative datasets, directly from hospitals, and through unions, c) conduct analyses of the association of outcomes with these measures, d) adapt methods of measuring nurses' working conditions, including nursing care organization, job strain, and risk of injury, to the hospital level, and e) conduct analyses of outcomes using this broader set of measures.